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removing black spots from concrete path

A load of black circles about the size of a penny have appeared all over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush, has
no effect. Bleach, even applied neat with a stiff brush, has no effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody else
has these, in fact I've never seen them before anywhere. Everyone else's
concrete paths have, to varying degrees, a uniform layer of black grime
that doesn't look too bad because its even, whereas the contrast I have
between clean concrete and black circles is rather unsightly.

"ben" wrote in message
...
A load of black circles about the size of a penny have appeared all over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush, has
no effect. Bleach, even applied neat with a stiff brush, has no effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody else
has these, in fact I've never seen them before anywhere. Everyone else's
concrete paths have, to varying degrees, a uniform layer of black grime
that doesn't look too bad because its even, whereas the contrast I have
between clean concrete and black circles is rather unsightly.

Any suggestions?

You could try a strong solution of Caustic soda or power jet wash if you
have one but I don't think you have otherwise you would have used it.

"ben" wrote in message
...
A load of black circles about the size of a penny have appeared all over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush, has
no effect. Bleach, even applied neat with a stiff brush, has no effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody else
has these, in fact I've never seen them before anywhere. Everyone else's
concrete paths have, to varying degrees, a uniform layer of black grime
that doesn't look too bad because its even, whereas the contrast I have
between clean concrete and black circles is rather unsightly.

Any suggestions?

==============
If you don't mind a rather wayout suggestion try wallpaper paste if you
have any left over from your last decorating job. Modern pastes usually
contain a fungicide and it might just give you some indication of what
you're dealing with. I've no idea if it will work but it's worth a try.
Alternatively look in your local Garden Centre for a proprietary garden
fungicide.

"ben" wrote in message
...
A load of black circles about the size of a penny have appeared all
over
my concrete garden path, obviously some kind of mould or fungus or
something.

snip
You could try a strong solution of Caustic soda or power jet wash if you
have one but I don't think you have otherwise you would have used it.

Pressure wash is unlikely to work on these spots. I have a few on some of
the slabs around my pool, and whilst an annual spring pressure wash will
remove most of the accumulated dirt and crap from the slabs, it doesn't
touch these spots. As Ben says, you're left with slabs that are nice and
clean with the spots standing out even more.

Yours can't be doing it's job then A 100 psi can take paint of window sills,
My backyard was covered in all sort of dirt, moss, oil stains fungi, when I
had finished the concrete was gleaming.

Try a toilet bowl cleaner or shower cleaner that contains acid. Put it on
the concrete for varying lengths of time and check its progress. If it is a
fungus, acid will usually get it out. Be sure and rinse it all off when you
are finished. Good luck. Dwayne

"Cicero" wrote in message
...

"ben" wrote in message
...
A load of black circles about the size of a penny have appeared all over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush, has
no effect. Bleach, even applied neat with a stiff brush, has no effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody else
has these, in fact I've never seen them before anywhere. Everyone else's
concrete paths have, to varying degrees, a uniform layer of black grime
that doesn't look too bad because its even, whereas the contrast I have
between clean concrete and black circles is rather unsightly.

Any suggestions?

==============
If you don't mind a rather wayout suggestion try wallpaper paste if you
have any left over from your last decorating job. Modern pastes usually
contain a fungicide and it might just give you some indication of what
you're dealing with. I've no idea if it will work but it's worth a try.
Alternatively look in your local Garden Centre for a proprietary garden
fungicide.

On Sat, 15 Mar 2003 14:24:32 +0000, ben wrote:
A load of black circles about the size of a penny have appeared all over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush, has
no effect. Bleach, even applied neat with a stiff brush, has no effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody else
has these, in fact I've never seen them before anywhere. Everyone else's
concrete paths have, to varying degrees, a uniform layer of black grime
that doesn't look too bad because its even, whereas the contrast I have
between clean concrete and black circles is rather unsightly.

Any suggestions?

There used to be an diesel Engine cleaner called "gunk" that is a petroleum
based liquid that will remove just about anything stuck to anything....

"wanderer" wrote in message
...
snip
You could try a strong solution of Caustic soda or power jet wash if
you
have one but I don't think you have otherwise you would have used it.

Pressure wash is unlikely to work on these spots. I have a few on some
of
the slabs around my pool, and whilst an annual spring pressure wash will
remove most of the accumulated dirt and crap from the slabs, it doesn't
touch these spots. As Ben says, you're left with slabs that are nice and
clean with the spots standing out even more.

Yours can't be doing it's job then A 100 psi can take paint of window
sills,
My backyard was covered in all sort of dirt, moss, oil stains fungi, when
I
had finished the concrete was gleaming.

That's rather presumptuous of you! As it happens my PW works fine, but the
spots seem to have some depth, as though they have etched into the slabs.

"Dwayne" wrote in message
...
Try a toilet bowl cleaner or shower cleaner that contains acid. Put it on
the concrete for varying lengths of time and check its progress. If it is
a
fungus, acid will usually get it out. Be sure and rinse it all off when
you
are finished. Good luck. Dwayne

"Cicero" wrote in message
...

"ben" wrote in message
...
A load of black circles about the size of a penny have appeared all
over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush,
has
no effect. Bleach, even applied neat with a stiff brush, has no
effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody
else
has these, in fact I've never seen them before anywhere. Everyone
else's
concrete paths have, to varying degrees, a uniform layer of black
grime
that doesn't look too bad because its even, whereas the contrast I
have
between clean concrete and black circles is rather unsightly.

Any suggestions?

==============
If you don't mind a rather wayout suggestion try wallpaper paste if you
have any left over from your last decorating job. Modern pastes usually
contain a fungicide and it might just give you some indication of what
you're dealing with. I've no idea if it will work but it's worth a try.
Alternatively look in your local Garden Centre for a proprietary garden
fungicide.

Cic.

I managed to remove mould spot on paving with steam. I used a wallpaper
remover to steam the slabs, The flat plate of the steamer was ideal, if a
little boring but the mould eventually lightened in colour and lost its grip
on the paving. A quick blast from a pressure washer then removed the mould.
I expect it will return after a while, but I'll be waiting..... with the
steamer.

Well, I tried a fungicide (dialkyldimethyl ammoniumchloride), or
'biocide' as they call it, which claims to work on fungi, mould, moss,
lichen, mildew and algae. Left on for 3 days then washed off as
directed. From all the warnings on the bottle it looks like nasty stuff
- shame the mould didn't seem to think so, its doing just fine :-(

Well, I tried a fungicide (dialkyldimethyl ammoniumchloride), or
'biocide' as they call it, which claims to work on fungi, mould, moss,
lichen, mildew and algae. Left on for 3 days then washed off as
directed. From all the warnings on the bottle it looks like nasty stuff
- shame the mould didn't seem to think so, its doing just fine :-(

Well Ben I am having the same problem. The cement lanai in the back of the house has had these black spots for the longest time. Pressure washing does not take them out,( they get a little lighter) . Tried chemicals, tried Clorox, but they just wore away at the layer of cement and now it's practically always gritty. I'm thinking possibly painting. Don't know what else to do!

A load of black circles about the size of a penny have appeared all over
my concrete garden path, obviously some kind of mould or fungus or
something. NOTHING seems to be able to get rid of them. Ordinary
potassium hydroxide patio cleaner, applied with a good stiff brush, has
no effect. Bleach, even applied neat with a stiff brush, has no effect.
I now have a path that looks cleaner than it did when it was new, but
the black spots are still there. Anyone able to suggest anything?

Incidentally, I've been looking around the neighbourhood and nobody else
has these, in fact I've never seen them before anywhere. Everyone else's
concrete paths have, to varying degrees, a uniform layer of black grime
that doesn't look too bad because its even, whereas the contrast I have
between clean concrete and black circles is rather unsightly.

Any suggestions?

[/quote] For Black Spots on your Patio, you need to buy Patio Black Spot Remover, from The Patio Black Spot Company Ltd ! Welcome to Patio Black Spot Removal. It is not cheap, but easy to use, with a pneumatic garden spray , HozeLock or similar, and a pressure washer. Not only does it kill and remove the Black Spots, it cleans and restores the Colour of the stone. Patio Black Spot Remover works on most stones, but is brilliant on Indian Sandstone. A gardener's dream. They also do a product which prevents the Black Spots coming back called, "Patio Black Spot Preventer". This you don't even have to wash off! Prepare to be amazed!